I probably will switch textbooks tomorrow because I’m getting bored.😀
Korean Grammar In Use – Beginning – English Version page 137 about -고 나서:
Further, when the subjects of the first and second clauses are the same in sentences using the motion verbs 가다 (to go), 오다 (to come), 들어가다 (to enter), 들어오다 (to exit), 나가다 (to leave), 나오다 (to emerge [from]), 올라가다 (to go up), and 내려가다 (to go down),
and the verbs 일어나다 (to get/stand up), 앉다 (to sit), 눕다 (to lie down), and 만나다 (to meet), 아/어서 is used in place of -고 and -고 나서.
나는 학교에 가고 나서 (나는) 공부해요. (x)
→ 나는 학교에 가서 (나는) 공부해요.(o)
I go to school and (I) study.
나는 오늘 버스에서 앉고 나서 (나는) 왔어요. (x)
나는 오늘 버스에서 앉아서 (나는) 왔어요. (o)
Today, (I) rode on the bus and (I) came (here).
But then I searched Google Books, words like 가고 나서, 만나고 나서, 눕고 나서, and all the verbs mentioned above are actually used (!) -even with the same subject for the first and second clause- to emphasize that something has happened “AFTER” something. So maybe… there are exceptions… Maybe it’s weird to simply say ‘I go to school and study’ using 가고 나서, but maybe it’s okay to say ‘AFTER I go to school, I (finally) study Korean’ using 가고 나서? Like this: 나는 학교에 가고 나서 (나는) 한국어를 배우게 되었다. Maybe?
And I think 들어오다 means “to come and enter”, not “exit”?
Suddenly I remember how I often got in trouble for asking too many questions in class. By the time I got into high school, I learned to be docile and dumb like everybody else, though. ###